(a) Field of the Invention
The present invention relates to a fungal MRP-like ABC transporter gene and organisms transformed with the gene, and more particularly, to transformed organisms expressing fungal MRP-like ABC transporter genes Including YCF1 or YHL035C, and thereby having improved resistance to and accumulation of toxic materials such as lead, cadmium, arsenic, and herbicides.
(b) Description of the Related Art
Heavy metals such as lead, cadmium, mercury and so on accumulate in the human body through nature's food chain and cause chronic damage to the brain, nerves, bones, etc., and the polluted environment and damage continues from generation to generation. Typical examples of problems caused by heavy metal toxicity are Minamata disease and Itaiitai disease, which have occurred in Japan. As lead is a pollutant that causes the most damage among the heavy metals (Salt, D. E., Smith, R. D., and Raskin, I. Phytoremediation. Annu. Rev. Plant Physiol. Plant Mol. Biol. 49, 643-668 (1998)), it is very important to rid lead from the environment. The United States government expends approximately 500 million dollars each year in order to remove lead from environments where children are raised (Lanphear, B. P. The paradox of lead poisoning prevention. Science. 281; 1617-1618 (1998)). Additionally, as arsenic pollutes drinking water and causes skin diseases and cancer, it is becoming a serious problem.
As known genes associated with resistance to or accumulation of toxic materials such as heavy metals and agricultural chemicals, bacterial P-type ATPase has a role in pumping lead to outside of cells at bacterial cell membranes (Rensing, C., Sun, Y., Mitra, B., and Rosen, B. P. Pb(II)-translocating P-type ATPases. J. Biol. Chem. 273: 32614-32617 (1998)); genes associated with cadmium resistance include the YCF1 gene of yeast; and genes associated with resistance to arsenic include the YCF1 and ACR genes of yeast, ArsAB of bacteria, etc.
Living organisms have a mechanism for mitigating toxicity of materials using transporter proteins or biological materials having affinity for noxious materials that invade the body. Use of genes contributing to living organism's resistance against noxious materials would provide an environmentally-friendly way to remediate environments polluted with noxious materials at a very low cost as compared with the physical and/or chemical remediation that is currently widely being employed (Mejare and Bulow, Trends in Biotechnology; 2001, Raskin I. and Ensley B. D. Phytoremediaton of Toxic Metals., John Wily & Sons, New York;2000). In particular, as plants have many advantages such as their ability to express foreign genes readily and thus exhibit new phenotypes, they can be produced and maintained at a low cost, they are aesthetically pleasing, etc., research on improvement of plants by inserting useful genes thereinto for use in environmental remediation is being actively conducted. This technique, the use of plants for cleaning up environment, is called “Phytoremediation.”
Under the circumstance where environmental pollution in soil, etc. due to toxic materials such as lead, cadmium, arsenic, and agricultural chemicals is serious, there is a great need for organisms that are transformed by genes that confer resistance to and/or accumulation of these toxic materials.
Transformed plants that can be used to remove cadmium from the environment have been disclosed in several papers (Zhu et al., (1999) Plant Physiol. 119: 73-79, Hirschi et al., (2000) Plant Physiol. 124:125-33, Dominguez-Solis et al., (2001) J. Biol. Chem. 276: 9297-9302), but there have been no report of transgenic plants that are enhanced in the capacity to remove lead or arsenic from the environment. Further, attempts to develop organisms transformed with YCF1 to improve resistance to not only lead but also to cadmium, arsenic, and herbicides for removal of these toxic materials have not yet been disclosed.